The invention refers to a position indicator for submerged valves, intended to provide as a result totally accurate and reliable remote signalling of the position of a valve submerged in a fluid (liquid or gas) in a tank or in any other volume of fluid, thereby guaranteeing the non-existence of erroneous signals, something that frequently occurs in the systems or devices that are currently used.
The indicator has been conceived for being applied preferably and fundamentally in hydraulic systems for the transfer of fluids so that the position of submerged valves can be known with reliability in the tanks of ships, thus permitting the correct functioning at all times of the hydraulic systems and preventing any incidents and/or accidents from occurring. Its application can be made to extend to any other practical situation in which their use is required, i.e., in all those cases in which it is necessary to know with reliability the position of a valve submerged in a fluid (liquid or gas).
Currently, the way to detect the position of submerged valves used in certain hydraulic systems for transferring and/or controlling fluids, is in most cases based on obtaining volumetric type signals, in other words, based on systems that relate the flow of hydraulic oil used as the drive element for the appropriate actuator for the valve, with the movement of the latter.
It is evident that, even in cases in which the system is functioning correctly, the position signal obtained can be distorted due to various reasons, with the consequence that the position reading of the valve provided by the system or device may not be correct. For example, expansions, minor leaks, etc., usually give rise to a distortion of the resulting position signal and therefore lead to a wrong reading, and the error becomes greater in cases in which the system is computer operated.
On the other hand, certain circumstances and actions, such as greater closure times in order to prevent excess pressure, greater sizes of valved and therefore larger actuators, can give rise to a flow that cannot prevent failure of the volumetric indicators (failures that lead to seizure, discontinuous readings, etc.), which can in turn lead to incidents or even accidents since in particular cases where they are being used in the tanks of ships this can cause the ship to list to one side, or it can cause the tanks to overflow, flooding of the ship, pollution, or apparatus or machines within reach of the flood or the overflow could break down or be put out of action.
DE Patent 1115090 discloses a position indicator for cut-off valves which uses a displaceable spindle wharve along the axis of the actuator shaft of the valve; the movement of the spindle wharve alters the position of a stem which finally produces an increase in the pressure of the hydraulic circuit.
The indicator of the invention is based on the fact that the signal by which the position reading of the submerged valve is obtained is transmitted by hydraulic pressure, with the particular feature that the unit formed from the indicator and components associated with it present certain structural and functional characteristics permitting the drawbacks referred to above to be solved, providing as a result a totally reliable signal, in other words, the position reading of the valve that it is sought to control is correct.
More specifically, the indicator itself consists of an actuator shaft by means of which the corresponding valve is opened and/or closed, and is operated by any suitable conventional system. In its operation, this shaft includes mechanical means capable of acting on one or more hydraulic cartridges in which regulation of the pressure takes place which in turn acts to regulate the pressure of a secondary hydraulic system, producing a pressure signal that is transmitted to a converter which transforms the signal into any kind of visible reading on a display screen, all this in such a way that the reading will correspond to the specific correct position of the valve.
By means of this indicator, the signal obtained remotely, and therefore the result of the reading of the valve position, is wholly reliable and accurate.
In a preferred embodiment of the invention, the mechanical means that acts on the hydraulic cartridges consists of cams secured to the actuating shaft, in such a way that as the shaft rotates the cams impinge on the hydraulic cartridge or cartridges in order to transmit the corresponding pressure signal to the position indicator of the valve.
In addition to the components and means that form part of the indicator and/or which are associated with it for its proper functioning, the indicator is also indirectly related to a main hydraulic unit and a control and command unit with the latter being connected to the actuator itself. The main hydraulic unit is intended to provide the hydraulic system with power and operation involved in the functioning of the valve via the actuator.
Among the advantages derived from the new conception of the position indicator of the invention, in addition to the fundamental advantage of reliability already referred to, mention can be made of the following:
Depending on the type of hydraulic cartridge used and an possible combinations thereof, an on-off reading can be obtained (open/closed valve) or a continuous reading, i.e., a reading of any intermediate position between the open/closed limits.
As well as being able to transmit the signal over long distances, given that it is a pressure transmission by hydraulic fluid, it can be used in certain types of installations or industries in which there exist zones classified as type xe2x80x9c0xe2x80x9d or the like, in other words, dangerous zones.
No kind of certification is required since the device does not contain any electrical components.
The pressure signal can be converted into an analog or digital signal by any conventional means in the control area, this aspect being compatible with any display system currently known.